Thermoset molding powders employing glycidyl methacrylate-functional polymers and monomeric anhydride crosslinking agents and moldings thereof

ABSTRACT

1. A MOLDING POWDER WHICH COMPRISES A PARTICULATE, INTIMATE MIXTURE OF (A) A COPOLYMER (1) CONSISTING OF ABOUT 15 TO ABOUT 40 WEIGHT PERCENT GLYCIDYL METHACRYLATE, ABOUT 10 TO ABOUT 30 WEIGHT PERCENT METHACRYLATE, AND A REMAINDER CONSISTING ESSENTIALLY OF METHYL METHACRYLATE, AND (2) HAVING AN AVERAGE MOLECULAR WEIGHT IN THE RANGE OF ABOUT 1,500 TO ABOUT 16,000, WITH LESS THAN 5 PERCENT OF THE MOLECULES OF SUCH COPOLYMER HAVING A MOLECULAR WEIGHT BELOW 1,000, A SOFTENING POINT ABOVE 25:C., AND EPOXIDE GROUPS IN ITS MOLECULAR STRUCTURE RESULTANT OF INCLUSION OF SAID GLYCIDYL METHACRYLATE AS A CONSTITUENT MONOMER THEREOF, AND (B) A MONOMERIC ANHYDRATE PRESENT IN AN AMOUNT WHICH PROVIDES ABOUT 0.5 TO ABOUT 1.5 ANHYDRIDE GROUPS PER EACH EPOXY GROUP IN THE MOLDING POWDER.

United States Patent 3,847,863 THERMOSET MOLDING POWDERS EMPLOYING GLYCIDYL METHACRYLATE-FUNCTIONAL POLYMERS AND MONOMERIC ANHYDRIDE CROSSLHNKING AGENTS AND MOLDINGS THEREOF Santolrh S. Labana, Dearborn Heights, and Ares N. Theodore, Farmington, Mich., assignors to Ford Motor Company, Dearborn, Mich.

No Drawing. Continuation of abandoned application Ser. No. 209,346, Dec. 17, 1971. This application Feb. 15, 1974, Ser. No. 443,184

Int. Cl. C08f 45/10 U.S. Cl. 260-42.].8 24 Claims ABSTRACT OF THE DISCLOSURE Novel thermosetting resin powders which can be molded to form products characterized, in fiexural measurement, by relatively high elongation-to-break, strength and modulus and by a high glass transition temperature are prepared from a mixture of a prepolymer consisting essentially of glycidyl methacrylate, methyl methacrylate and methacrylonitrile or acrylonitrile and an anhydride crosslinking agent.

This is a continuation of application Ser. No. 209,346, filed Dec. 17, 1971, and now abandoned.

THE INVENTION This invention relates to self-crosslinking, dry thermo settable molding powders suitable for rapid curing during processing as by compression and injection molding and applicable to the production of rigid, tough, structural materials as, for instance, automobile body panels, electrical'appliance housings, boat construction, storage tanks, conduits, particularly those for the transmission of heated fluids, etc., and to molded articles produced therefrom.

The thermosets of this invention, after molding, have a glass transition temperature above 90 C., preferably above 120 C. At room temperature (20-25 C.) these moldings exhibit, in flexural measurement, a strength in the range of about 16,000 to about 30,000 p.s.i. or higher, a modulus in the range of about 1.2-2.25 10 p.s.i. or higher and elongation-to-break in the range of about 1 to about 3% or higher.

Glass transition temperature is that temperature at which a glass-like material loses its rigidity and hardness and approaches the behavior of an elastomer. More specifically, glass transition temperature is defined as the temperature at which such material shows a maximum in its mechanical damping at low frequencies, e.g., about 1 cycle per second.

(I) Composition of the Prepolymer The prepolymer preferably has at least three constituent monomers and, except for limited substitution as hereinafter noted, has the following basic composition:

Glycidyl methacrylate -40, preferably -35 wt. percent. Methacrylonitrile 0-30, preferably 10-25 wt. percent. Methyl methacrylate Balance.

Acrylonitrile may be substituted in whole or in part for the methacrylonitrile but the latter is the preferred reactant in that products produced from prepolymers containing this constituent and the crosslinking agents used herein have a higher heat distortion (glass transition) temperature than do the corresponding products using acrylonitrile, all other factors being equal.

A minor portion of the methyl methacrylate, preferably ice not more than thereof, may be replaced with styrene, alpha methyl styrene, vinyl acetate or a different ester of acrylic or methacrylic acid and monohydric alcohol, preferably a C -C alcohol, e.g., ethyl acrylate, butyl acrylate, butyl methacrylate, etc. This substitute should not exceed about 15 percent of the total monomers used to form the prepolymer and preferably does not exceed 10% of the same. In the case of the C substitutes, this component preferably does not exceed /5 of the methyl methacrylate. The substitutes mentioned in this paragraph, with the exception of styrene, increase the flexibility of the polymer, i.e., the elongation-to-break factor, and decrease the softening point (glass transition temperature).

(II) Properties of the Prepolymer The prepolymer has an average molecular weight in the range of about 1,500 to about 16,000, preferably about 2,000 to about 10,000, and more preferably about 3,500 to about 8,000, as determined by vapor phase osmometry using methyl ethyl ketone as solvent. Less than about 5% of the molecules thereof should have a molecular weight below about 1,000.

The prepolymer has a softening point above 25 C., preferably in the range of about 50 to about C.

(III) Preparation of the Prepolymer The prepolymer is advantageously formed by solution polymerization using heat, a free radical initiator and an inert solvent. The prepolymer is preferably recovered by coagulation. Hexane, a mixture of hexane and toluene, etc., are suitable for this purpose. It may be recovered by evaporation but if this embodiment is used the product should be washed with a suitable solvent to remove low molecular weight components.

A free radical initiator is dissolved in the combined monomeric reactants and is advantageously employed in an amount equal to about l-4 wt. percent of the combined monomer weight. Conventional free radical initiators are suitable for this purpose, e.g., acylperoxides, peresters, and azo compounds. Specific materials which have been used successfully include 2,2'-azobis (2-methyl propionitrile) hereinafter termed AIBN, benzoyl peroxide, t-butyl perbenzoate, and t-butyl peroxypivalate.

As aforementioned, the reaction is carried out in an inert solvent, e. g., toluene or a mixture of toluene and dioxane, etc. Advantageously, the weight of the solvent is equal to or in excess of the combined weight of the reactant and the initiator.

In a preferred method of preparation, the monomeric reactants and the free radical initiator are added in small increments, e.g., dropwise, to the solvent heated to reflux under nitrogen. When addition is complete, initiator in the amount of about 0.1% monomer weight is dissolved in a small amount of solvent and added over a period of 20-60 minutes. The reflux is then continued for about 2 hours. The prepolymer is then recovered by coagulation. This is preferably effected in the following manner. The reaction solution is further diluted with additional solvent until the prepolymer comprises about 20 to about 30 weight percent of the resultant solution. This solution is then added slowly to a liquid that will effect precipitation of the prepolymer. In this instance, hexane is quite suitable. A fine powder precipitates. This is recovered by filtration, dried, and, if necessary, broken up by rolling or grinding.

In addition to the aforedescribed method of prepolymer preparation, the prepolymer can be formed by the Wellknown techniques of emulsion polymerization, bulk polymerization and suspension polymerization. Suspension polymerization is preferably carried out using water as the suspending medium. Since ionic stabilizers react with glycidyl methacrylate, only nonionic materials may be used for stabilizing the suspension. Polyvinyl alcohol and an alkyl aryl polyether alcohol (Triton X 100--Rohm & Haas Co.) have been found quite satisfactory. To carry out suspension polymerization, the monomer mixture is added to cooled (about C.) 0.1% solution of polyvinyl alcohol in water. The mixture is stirred rapidly and the initiator added over a period of about 30 minutes. The temperature of the reaction mixture is then controlled to remain between 55 and 60 C. for six to eight hours. After cooling to room temperature, the polymer is collected by filtration. Because the polymerization must be carried out below 65 C., only the initiators which are an efiicient source of free radicals below this temperature may be used. Suitable initiators for suspension polymerization include t-butyl peroxypivalate and diisopropyl peroxycarbonate. The molecular weight of the prepolymer can be controlled, among other ways, by using 0.1 to about weight percent (based on monomer weight) of a chain transfer agent such as lauryl mercaptan.

(IV) Crosslinking Agent The crosslinking agent of this thermoset system is a monomeric anhydride. Among the anhydrides which are useful in this invention are the anhydrides of the following three classifications:

(1) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhydride group is directly attached to one of a pair of carbon atoms which are directly attached to and adjacent to each other, e.g., succinic anhydride, citraconic anhydride, 1,2-dimethyl succinic anhydride, and dodecyl succinic anhydride,

(2) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhydride group is directly attached to one of a pair of carbon atoms which are not directly attached to and adjacent to each other (i.e., separated by at least one carbon atom), e.g., glutaric anhydride, 1,2-dirnethyl glutaric anhydride, and 1,3-dimethyl glutaric anhydride, and

(3) monomeric anhydrides of cyclic di-, tri-, or tetracarboxylic acids wherein each carbon atom of an anhydride group is directly attached to one of a pair of directly attached and adjacent carbon atoms of a C C ring structure.

(a) where the ring is aromatic this embodiment is exemplified by phthalic anhydride, trimellitic anhydride, dimellitic anhydride, and naphthalene tetracarboxylic dianhydride, (b) where the ring is a saturated, aliphatic (carbon-to-carbon) ring, this embodiment is exemplified by hexahydrophthalic anhydride, cyclooctane- 1,2-dicarboxylic anhydride, and cyclobutane dicarboxylic anhydride.

(c) where the ring is an unsaturated, aliphatic (carbon-to-carbon) ring, this embodiment is exemplified by tetrahydrophthalic anhydride,

(d) where the ring is heterocyclic, this embodiment is exemplified by tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, 7 oxabicyclo [2.2.1] heptane-2,3-dicarboxylic anhydride, and 7-heptane- 2,3-dicarboxylic anhydride, and 7-oxabicyclo [2.2.1.] hept-5-ene-2,3-dicarboxylic anhydride.

It will be understood by those skilled in the art that the afore-listed monomeric anhydrides may have a hydrogen atom replaced with a methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy or butoxy group or a halogen atom. In the case of the heterocyclic anhydrides, a ring substitution for a carbon atom may be by an oxygen atom, a sulfur atom, a divalent silicon radical or a divalent phosphorous radical. The anhydride is employed in a quantity sufficient to provide about 0.5 to about 1.5 preferably 0.6 to 0.9, anhydride groups for each epoxy group in the molding powder.

(V) Partial Replacement for Prepolymer With Epoxy Compound A minor portion, i.e. about 2 to about 20 percent, of the epoxy groups provided by the prepolymer may be replaced by substituting for that amount of the prepolymer an epoxy compound having at least two epoxy groups, preferably a diepoxide.

These diepoxides should be liquid at 140 C. or below and have molecular weight in the range of about 300 to about 4,000 and viscosity at 140 C. of less than 50 poises.

The diepoxide may be an aromatic, an acyclic aliphatic or cycloaliphatic diepoxide. Such diepoxides should consist essentially of carbon, hydrogen and oxygen but may have substituents which do not interfere with the crosslinking reactions, e.g. sulfonyl groups, nitro groups, alkylthio groups and halogens.

These diepoxides are well known in the art and many are commercially available. Typical examples include diglycidyl esters of polybasic or dibasic acids as disclosed in U.S. Pat. No. 2,866,767; diglicidyl ethers are dihydric phenols as disclosed in U.S. Pats. Nos. 2,467,171; 2,506,486; 2,640,037; and 2,841,595; diglycidyl ethers of diols as disclosed in U.S. Pats. Nos. 2,538,072 and 2,581,464 and diepoxides obtained by peracid epoxidation of dienes. A collection of suitable diepoxides are illustrated in U.S. patent application Ser. No. 43,895, filed June 5, 1970 and these disclosures are incorporated herein by reference. Although the diepoxides are to be preferred for the present invention, low viscosity polyepoxides may also be advantageously used.

(VI) Catalysts A catalyst is employed in the molding powder mix to facilitate the crosslinking reaction. Quaternary ammonium salts exhibit a high degree of specificity for the epoxyanhydride reaction. These include tetrabutyl ammonium iodide, chloride, bromide, tetraethyl ammonium iodide, chloride and bromide, tetramethyl ammonium bromide, chloride and iodide, benzyl trimethyl ammonium iodide, chloride and bromide, benzyl dimethyl phenyl ammonium chloride, bromide and iodide, stearyl dimethyl benzyl ammonium iodide, bromide and cholride, etc. Catalysts of this type are useful at levels of about 0.05 to about 1.0 wt. percent of the combined reactants.

Other catalysts which may be used include solid tertiary amines such as triethylene diamine, amine salts such as trimethylamine-p-toluene sulfonate or imidazoles such as 2-ethyl-4-methyl imidazole or metal carboxylates such as lithium benzoate. Catalysts of these types are useful at the same concentration levels above set forth.

These catalysts are found to be latent catalysts for anhydride epoxy reactions. That is to say that the catalysts do not significantly enhance the rate of reaction at room temperature but are effective only above certain temperatures. The catalysts that are latent up to at least 50 C. are preferred.

(VII) Preparation of the Molding Powder Mix The powdered prepolymer, the crosslinking agent and the catalyst are dissolved in a suitable solvent, e.g., acetone, methylene chloride, benzene, etc., and the solution is thoroughly stirred. The solvent is evaporated under vacuum leaving a solid cake which is crushed to a fine powder. The powder is further dried under vacuum so that it contains less than one percent of the solvent.

Alternatively, to the prepolymer solution as obtained by polymerization are added crosslinking agent and the catalyst. The solution is stirred until homogeneous and then added slowly to a vigorously stirred precipitating solvent such as hexane. The precipitated powder is dried under vacuum. To ensure its homogeneity, the molding powder is passed through a roll mill at 50 to C. In lieu of employing the precipitation solvent and roll mill,

one may merely evaporate the solvent of the prepolymer solution.

Another method of preparing the molding powder consists of mixing together the powdered prepolymer, crosslinking agent, and catalyst and homogenizing by passing through an extrusion mixer or a roll mill.

If desired, reinforcing fillers such as asbestos, glass fibers, clay, calcium carbonate, calcium silicate, etc., may also be incorporated in the molding powders. A particularly effective filler is calcium metasilicate (CaSiO The powders thus prepared are suitable for use in injection molding, compression molding and transfer molding.

This invention will be more fully understood from the following illustrative examples wherein flexural properties of the molded specimens are determined by Flexural Test, American Society of Testing & Materials, D790-1966. In this test rectangular bars having thickness inch, width 0500-0600 inch and length 4 inches are used for determining the flexural properties. A table model Instron Mechanical testing machine is used herein for testing. It is set up at a crosshead speed of 0.04 in./min. and a recorder chart speed of 2 inches/min. The formulas in procedure B (ASTM D790-66) are used for the calculation of flexural modulus, elongation-to-break and strength.

The prepolymers in the foregoing illustrative examples have softening points between 50 and 110 C. with less than 5% of the molecules thereof having molecular weight below 1,000. The molded articles of all such examples have glass transition temperatures above 90 C.

Example 1 A prepolymer is prepared from the following components in the manner hereinafter set forth:

AIBN, i.e., 2,2'-azobis-(Z-methylpropionitrile), in the amount of 54 grams (3%) is added to the monomer mixture. This solution is added dropwise over a 4 hour period into 1950 ml. toluene at 108 -111 C. under nitrogen atmosphere. Then 2.0 grams of AIBN dissolved in ml. acetone are added over a /2 hour period and refluxing continued for 3 additional hours.

The polymer solution is diluted with 3,000 ml. acetone and coagulated in hexane. The white powder is dried in a vacuum oven at 70 C. for 35 hours. Its molecular weight is found to be M /M =6231/ 3466 with a molecular weight per epoxide unit, hereinafter referred to as WPE, of 496.

This prepolymer is used in the preparation of molding powder. In this process, 35.0 grams of the prepolymer are combined with 10.7 grams of tetrahydrophthalic anhydride and 0.046 grams tetrabutyl ammonium iodide and ballmilled for 16 hours. Then, 28.0 grams of this powder are combined with 32.0 grams of calcium metasilicate (CaSiO and ball-milled for two hours. The resulting mix is blended with 20.0 grams chopped glass fibers A inch average lengthall chopped glass fibers used in succeeding examples are of this length). After combining the molding powder with the chopped glass fibers, the mixture is tumbled. This ensures mixing all components without fiber damage. Then a preform is made for molding.

A sheet (4.7 x 5.2 x inches--all sheets molded in succeeding examples are of these dimensions) is molded from this powder and fiber mix by compressing the mix at a pressure of 1500 p.s.i. at a temperature of 380 F. for minutes.

This molding exhibits the following flexural properties:

Flexural strength, p.s.i 25,000 Elongation-to-break, percent 2.0 Flexural modulus, p.s.i 2.2 10

This molding powder is found to be processable, i.e., in condition for carrying out the aforecited procedures, after standing at room temperature for 3.5 months.

Example 2 The prepolymer of Example 1 in the amount of 35.0 grams is mixed with 7.1 grams of succinic anhydride and 0.058 grams tetrabutyl ammonium chloride. After ballmilling this mix for 16 hours, 28.0 grams of this mixture are mixed With 32.0 grams of calcium metasilicate and ball-milled for two hours. The resulting mix is blended with 20.0 grams chopped glass fibers. After combining the molding powder with the chopped glass fibers, the mixture is tumbled to distribute the glass fibers and a preform is made for molding.

A sheet of this material is molded under identical molding conditions as those employed in Example 1. This sheet is found to have the following flexural properties:

Flexural strength, p.s.i 22,100 Elongation-to-break, percent 1.7 Flexural modulus, p.s.i 2.04 10 Example 3 The prepolymer of Example 1 in the amount of 25.0 grams is mixed with 7.5 grams phthalic anhydride and 0.049 grams tetrabutyl ammonium bromide. After ballmilling ingredients for 16 hours, 32.5 grams of the molding powder is mixed with 37.0 grams calcium metalsilicate and 23.2 grams of chopped glass fibers and processed using the identical procedure used in the preceding examples.

A sheet molded from this material and formed by using the identical molding conditions used in Example 1 has the following flexural properties:

Flexural strength, p.s.i 24,000 Elongation-to-break, percent 1.9 Flexural modulus, p.s.i 1.85 10 Example 4 The prepolymer of Example 1 in the amount of 25.0 grams is combined with 6.6 grams of glutaric anhydride and 0.32 grams tetraethyl ammonium bromide. After ballmilling the ingredients for 1.6 hours, 28 grams of this molding powder are processed by the identical procedure used in Example 1 with 32 grams of calcium metasilicate and 20.0 grams of chopped glass fibers. A sheet is molded using the identical molding conditions used in Example 1. This sheet is found to have the following flexural properties:

Flexural strength, p.s.i 22,400

Elongation-tobreak, percent 1.5

Flexural modulus, p.s.i 2.03 10 Example 5 The prepolymer of Example 1 in the amount of 25.0 grams is combined with 7.7 grams of hexahydrophthalic anhydride and 0.0033 grams tetramethyl ammonium io dide. After dry blending ingredients by ball-milling for 15 hours, 28.0 grams of this molding powder are processed using the identical procedure used in Example 1 with 32.0 grams of calcium metasilicate and 20.0 grams of chopped glass fibers. A sheet is molded using the identical molding conditions used in Example 1 is found to have the following flexural properties:

Flexural strength, p.s.i 24,500 Elongation-to-break, percent 1.8 Flexural modulus, p.s.i 2.02 x10 'Example 6 The prepolymer of Example 1 in the amount of 25.0 grams is combined with 5.0 grams trimellitic anhydride and 0.030 grams benzyl dimethyl phenyl ammonium chlo ride. After dry blending the ingredients by ball-milling for 15 hours, 28.0 grams of this molding powder mix are processed with 32.0 grams calcium metasilicate and 20.0 grams chopped glass fibers using the identical procedure used in Example 1. A sheet is compression molded using the identical conditions used in Example 1.

Example 7 The procedure of Example 1 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of p-chlorophthalic anhydride.

Example 9 The procedure of Example 1 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of tetrabromophthalic anhydride.

Example 10 The procedure of Example 1 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of methyl succinic anhydride.

Example 11 The procedure of Example 1 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of 4,4'-(2-acetoxy-l,3- glyceryl) bisanhydro-trimellitic anhydride.

Example 12 The procedure of Example 1 is repeated except for the difference that the calmium metasilicate is replaced with 40 grams of calcium carbonate.

Example 13 The procedure of Example 1 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with tetrahydrofuran-2,3,4,S-tetracarboxylic dianhydride in an amount such as to provide a number of anhydride groups equal to the number replaced.

Example 14 The procedure of Example 1 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced by an equimolar amount of 7-oxabicyclo[2.2.1.] hept-S-ene-Z,3-dicarboxylic anhydride.

Example 15 The procedure of Example 1 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of 7-oxabicyclo[2.2.1] heptane-2,3-dicarboxylic anhydride.

Example 16 The procedure of Example 1 is repeated except for the difference that the amount of calcium metasilicate employed is grams.

Example 17 The procedure of Example 1 is repeated except for the difference that the prepolymer is formed from 40 Weight percent glycidyl methacrylate and 60 weight percent methyl methacrylate and the quantity of anhydride used is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

8 Example 18 The procedure of Example 1 is repeated except for the difference that the prepolymer is formed from weight percent glycidyl methacrylate, 25 weight percent methacrylonitrile and weight percent methyl methacrylate and the quantity of anhydride is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

Example 19 The procedure of Example 1 is repeated with the difference that the prepolymer is formed from 30 weight percent glycidyl methacrylate, 20 weight percent methacrylonitrile and 50 weight percent methyl methacrylate and the quantity of anhydride is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

Example 20 The procedure of Example 1 is repeated with the difference that the prepolymer is formed from 30 weight percent glycidyl methacrylate, 20 weight percent acrylonitrile and 50 weight percent methyl methacrylate and the quantity of anhydride is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

Example 21 The procedure of Example 1 is repeated with the difference that the prepolymer is formed from 20 weight percent glycidyl methacrylate, 25 weight percent methacrylonitrile, 5 weight percent butyl acrylate, 5 Weight percent butyl methacrylate, 5 weight percent 2-ethyl hexyl acrylate and 40 weight percent methyl methacrylate and the quantity of anhyride is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

Example 22 The procedure of Example 1 is repeated with the difference that the prepolymer is formed from 15 weight percent glycidyl methacrylate, 30 weight percent methacrylonitrile and 55 weight percent methyl methacrylate and the quantity of anhydride is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

Example 23 The procedure of Example 1 is repeated with the difference that the prepolymer is formed from 35 weight percent glycidyl methacrylate, 10 weight percent methacrylonitrile, 10 weight percent styrene and Weight percent methyl methacrylate and the quantity of anhydride is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

Example 24 The procedure of Example 1 is repeated with the difference that the prepolymer is formed from 15 weight percent glycidyl methacrylate, 30 weight percent methacrylonitrile, and 55 weight percent methyl methacrylate and the quantity of anhydride is adjusted to compensate for the change in the number of epoxy groups in the prepolymer.

Example 25 The procedure of Example 1 is repeated with the difference that the prepolymer is formed from 20 weight percent glycidyl methacrylate, 30 weight percent acrylonitrile and weight percent methyl methacrylate and the quantity of the anhydride is adjusted to compensate for the change in the number of epoxy groups in the pre polymer.

Example 26 The procedure of Examples 1-10 inclusive are repeated with the difference that the anhydride is employed in an amount which provides 0.5 anhydride groups per each epoxy group in the thermoset molding powder.

9 Example 27 Example 28 The procedure of Example 1 is repeated with the difference that the molecular weight (M of the prepolymer is about 1,500.

Example 29 The procedure of Example 1 is repeated with the difference that the molecular weight (M of the prepolymer is about 2,000.

Example 30 The procedure of Example 1 is repeated with the difference that the molecular weight (M of the prepolymer is about 3,000.

Example 31 The procedure of Example 1 is repeated with the difference that the molecular weight (M of the prepolymer is about 6,000.

Example 32 The procedure of Example 1 is repeated with the difference that the molecular weight (M of the prepolymer is about 10,000.

Example 33 The procedure of Example 1 is repeated except for the difference that the molecular weight (M,,) of the prepolymer is about 16,000.

Example 34 The procedure of Example 1 is repeated except for the difference that in the production of the prepolymer 25 weight percent of the methyl methacrylate is replaced with an equimolar amount of styrene.

Example 35 The procedure of Example 1 is repeated except for the difference that in the production of the prepolymer 25 weight percent of the methacrylonitrile is replaced with an equimolar amount of acrylonitrile.

Example 36 The procedure of Example 1 is repeated except for the difference that in the production of the prepolymer 50 weight percent of the methacrylonitrile is replaced with an equimolar amount of acrylonitrile.

Example 37 The procedure of Example 1 is repeated except for the difference that in the production of the prepolymer 75 weight percent of the methacrylonitrile is replaced with an equimolar amount of acrylonitrile.

Example 38 The procedure of Example 1 is repeated except for the difference that in the production of the prepolymer 25 weight percent of the methyl methacrylate is replaced with an equimolar amount of alpha methyl styrene.

Example 39 The procedure of Example 1 is repeated except for the difference that the amount of catalyst employed in preparation of the molding powder is 0.05 weight percent of the combined weights of the reactants.

Example 40 The procedure of Example 1 is repeated except for the difference that the amount of catalyst employed in pre aration of the molding powder is 0.25 weight percent of the combined weights of the reactants.

10 Example 41 The procedure of Example 1 is repeated with the difference that the amount of catalyst employed in preparation of the molding powder is 0.5 weight percent of the combined weights of the reactants.

Example 42 The procedure of Example 1 is repeated except for the difference that the amount of catalyst employed in preparation of the molding powder is 1.0 weight percent of the combined weights of the reactants.

Example 43 A solid epoxy resin in the amount of 7.0 grams is melted and 11 grams of tetrahydrophthalic anhydride are added with stirring. The temperature is maintained at 100 C. for 1 hour. The blend or adduct-blend is quite fluid at C. The blend or adduct-blend is allowed to cool and solidify. It is then ground to a fine powder. The molding powder is made up by combining 17.0 grams of the prepolymer of Example 1, 11.0 grams of the blend or adduct-blend and 0.028 grams tetrabutyl ammonium iodide. After bal1-milling the ingredients for 16 hours, 28.0 grams of the molding powder are processed with 32.0 grams calcium metasilicate and 20.0 grams chopped glass fibers following the identical procedure used in Example 1.

A sheet is compression molded from the powder using the identical molding conditions used in Example 1. This sheet has the following flexural properties:

Flexural strength, p.s.i 27,220 Elongation-to-break, percent 1.7 Flexural modulus, p.s.i 2.25 10 The epoxy resin used in this example is a commercially available diepoxide having the following typical properties: melting point about 64-76 C., epoxide equivalent about 450-525, and average molecular weight of about 900.

This diepoxide is represented by the following structural formula wherein n =2z The procedure of Example 43 is repeated except that an amount of the prepolymer providing 2 percent of the epoxy groups is replaced with the diepoxide of Example 43 employed in an amount providing the same number of epoxy groups.

Example 45 The procedure of Example 43 is repeated except that an amount of the prepolymer providing 10 percent of the epoxy groups is replaced with the diepoxide of Example 43 employed in an amount providing the same number of epoxy groups.

Example 46 The procedure of Example 46 is repeated except, that an amount of the prepolymer providing 20 percent of the epoxy groups is replaced with the diepoxide of Example 43 employed in an amount providing the same number of epoxy groups.

1 1 Example 47 The procedure of Example 43 is repeated except that an equimolar amount of an aliphatic diepoxide is substituted for the aromatic diepoxide used in Example 43. This aliphatic diepoxide is synthesized in the following manner: to a 2,000 ml., 3-neck flask equipped with stirrer, dropping funnel, thermometer and nitrogen inlet, is added 1 mole of 2,3-butanediol (91.12 gms.) and 4 moles of epichlorohydrin (370 gms.). The temperature is maintained at 110 C. while 2 moles sodium hydroxide (80.0 gms.) is added dropwise as a 30% aqueous solution. The rate of addition is regulated so that the reaction mixture remains neutral. After about 3 hours, the organic layer is separated, dried, distilled, and a polymer is recovered. This The procedure of Example 43 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of succinic anhydride.

Example 49 The procedure of Example 43 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of glutaric anhydride.

Example 50 The procedure of Example 43 is repeated except for the difference that the tetrahydrophthalic anhydride is replaced with an equimolar amount of phthalic anhydride.

Example 51 A prepolymer is prepared using the identical procedure used to prepare the prepolymer of Example 1 from the following monomers employed in the following proportions:

Wt. percent Glycidyl methacrylate 3O Methacrylonitrile 18 Methyl methacrylate 52 AIBN 1.5

Molecular weight is controlled by using about 2 Wt. percent basis combined weight of reactants of lauryl mercaptan.

The resultant prepolymer has molecular weight of M /M 8564/4674 and WPE of 474. A molding powder mix is prepared by ball-milling for hours 100.0 grams of the copolymer with 32.1 grams of tetrahydrophthalic anhydride and 0.250 grams triethylene diamine. This mix in the amount of 28.0 grams is processed with 32.0 grams calcium metasilicate and 20.0 grams chopped glass fibers according to the identical procedure of Example 1.

A sheet is compression molded from this mix using the identical molding conditions used in Example 1.

This sheet has the following fiexural properties:

Flexural strength, p.s.i 24,642

Elongation-to-break, percent 1.82

Flexural modulus, p.s.i 2.17 10 Example 52 The procedures of Examples 1 and 43 are repeated with the difference that the tetrabutyl ammonium iodide is replaced by an equimolar amount of tetramethyl ammonium chloride.

Example 53 The procedures of Examples 1 and 43 are repeated with the difference that the tetrabutyl ammonium iodide is replaced by an equimolar amount of tetraethyl ammonium bromide.

Example 54 The procedures of Examples 1 and 43 are repeated with the difference that the tetrabutyl ammonium iodide is replaced by an equimolar amount of tetrabutyl ammonium iodide.

Example 55 The procedures of Examples 1 and 43 are repeated with the dilference that the tetrabutyl ammonium iodide is replaced by an equimolar amount of benzyl dimethyl phenyl ammonium iodide.

Example 5 6 A thermoset molding is prepared without filler in the following manner: The prepolymer of Example 1 in the amount of 100.0 grams is mixed with 32.07 grams tetrahydrophthalic anhydride, and 0.250 grams triethylene diamine. After ball-milling the components for 15 hours, the molding powder mix is molded under the identical conditions of compression molding used in Example 1. This molded sheet is found to have the following fiexural properties:

Flexural strength, p.s.i 16,300

Elongation-to-break, percent 3.1

Flexural modulus, p.s.i 582,835

Example 57 The procedures of Examples 1 and 43 are repeated with the difference that the anhydride is employed in an amount which provides 0.6 anhydride groups per each epoxy group in the thermoset molding powder.

Example 58 The procedure of Examples 1 and 43 are repeated with the dilference that the anhydride is employed in an amount which provides 0.9 anhydride groups per each epoxy group in the thermoset molding powder.

Example 59 A monomer mixture having the following composition is prepared from the following:

Wt. percent Glycidyl methacrylate 15 Methyl methacrylate 57 -Isobornyl methacrylate 28 Polymerization is carried out using the identical procedure used in Example 1 except that the concentration of AIBN catalyst employed is 1% (basis weight of reactants). The resultant prepolymer has a T (glass transition temperature) of about C. and an average molecular weight of about 8,500.

This prepolymer in the amount of 30.0 grams is mixed with 2.1 grams of glutaric anhydride and 0.0320 grams tetrapropyl ammonium iodide. This mixture is dry blended by ball-milling for 15 hours and processed using the identical procedure used in Example 1 and compression molded into a sheet using the identical molding conditions employed in Example 1.

Example 60 A monomer mixture having the following composition is prepared from the following:

Polymerization is carried out using the identical procedure used in Example 1 except that the concentration 13 of AIBN catalyst employed is 1% (basis weight of reactants). The resultant prepolymer has a T of 50 C. and an average molecular weight of about 8,500.

This prepolymer in the amount of 30 grams is mixed with 2.5 grams of succinic anhydride and 0.033 grams benzyl dimethyl phenyl ammonium chloride. After dry blending the ingredients by ball-milling for hours the powder is processed using the identical conditions used in Example 1 and compression molded into a sheet using the identical molding conditions employed in Example 1.

The foregoing examples are illustrative of the invention defined in the appended claims. Those skilled in the art will be aware that modifications may be made in such examples without departing from the scope of the invention as set forth in the general disclosure and the appended claims.

What is claimed is:

1. A molding powder which comprises a particulate, intimate mixture of (a) a copolymer (1) consisting of about 15 to about 40 weight percent glycidyl methacrylate, about 10 to about 30 weight percent methacrylonitrile, and a remainder consisting essentially of methyl methacrylate, and

(2) having an average molecular weight in the range of about 1,500 to about 16,000, with less than 5 percent of the molecules of such copolymer having a molecular weight below 1,000, a softening point above 25 C., and epoxide groups in its molecular structure resultant of inclusion of said glycidyl methacrylate as a constituent monomer thereof, and

(b) a monomeric anhydride present in an amount which provides about 0.5 to about 1.5 anhydride groups per each epoxy group in the molding powder.

2. A molding powder in accordance with Claim 1 wherein said copolymer has an average molecular weight in the range of about 2,000 to about 10,000.

3. A molding powder in accordance with Claim 1 wherein said copolymer has an average molecular weight in the range of about 3,5 00 to about 8,000.

4. A molding powder in accordance with Claim 1 wherein said monomeric anhydride is selected from (1) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhydride group is directly attached to one of a pair of carbon atoms which are directly attached to and adjacent to each other,

(2) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhydride group is directly attached to one of a pair of carbon atoms which are separated by at least one carbon atom, and

(3) monomeric anhydrides of cyclic di-, tri-, or tetracarboxylic acids wherein each carbon atom of an anhydride group is directly attached to one of a pair of directly attached and adjacent carbon atoms of a C C ring structure.

5. A molding powder in accordance with Claim 1 wherein said anhydride is employed in an amount which provides about 0.6 to about 0.9 anhydride groups per each epoxy group in the molding powder.

6. A molding powder in accordance with Claim 1 wherein, in addition to said epoxy-functional copolymer of acrylic monomers, there is employed an epoxy-functional compound including at least two epoxy groups which has a molecular weight in the range of about 300 to about 4,000 and a viscosity at 140 C. of less than 50 poises, said epoxy-functional compound being of difierent composition than said copolymer and being employed in an amount providing about 2 to about percent of the epoxy groups in said molding powder.

7. A molding powder in accordance with Claim 1 14 wherein said epoxy-functional copolymer of acrylic monomers consists essentially of about 20 to about 35 weight percent glycidyl methacrylate, about 10 to about 25 weight percent methacrylonitr-ile and a remainder consisting essentially of methyl methacrylate.

8. A molding powder in accordance with Claim 1 wherein at least a min-or portion but not more than /3 of said methyl methacrylate is replaced with a monomer selected from the group consisting of styrene, alphamethyl styrene, vinyl acetate and an ester of acrylic or methacrylic acid and a monohydric alcohol other than methanol.

9. A molding powder in accordance with Claim 1 wherein particulate, reinforcing filler is intimately dispersed with said copolymer and said monomeric anhydride.

10. A molding powder which comprises a particulate, intimate mixture of (a) a copolymer (1) consisting of about 20 to about 35 weight percent glycidyl methacrylate, about 10 to about 25 weight percent methacrylonitrile, and a remainder consisting essentially of methyl meth' acrylate, and

(2) having an average molecular weight in the range of about 2,000 to about 10,000, with less than 5 percent of the molecules of said copolymer having a molecular weight below 1,000, a softening point above 25 C., and epoxide groups in its molecular structure resultant of inclusion of said glycidyl methacrylate as a constituent monomer thereof, and

(b) a monomeric anhydride present in an amount which provides about 0.5 to about 1.5 anhydride groups per each epoxy group in the molding powder, said anhydride being selected from (3) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhydride group is directly attached to one of a pair of carbon atoms which are directly attached to and adjacent to each other,

(2) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhy dr'ide group is directly attached to one of a pair of carbon atoms which are separated by at least one carbon atom, and

(3) monomeric anhydrides of cyclic, di-, tri-, or tetra-canboxylic acids wherein each carbon atom of an anhydride group is directly attached to one of a pair of directly attache-d and adjacent carbon atoms of a C C ring structure.

11. A molding powder in accordance with Claim 10 wherein said copolymer has an average molecular weight in the range of about 3,500 to about 8,000.

12. A molding powder in accordance with Claim 10 wherein, in addition to said epoxy functional copolymer of acrylic monomers, there is employed a diepoxide of different composition than said copolymer which has a molecular weight in the range of about 300 to about 4,000 and a viscosity at C. of less than 50 poises, said diepoxide being employed in an amount providing about 2 to about 20 percent of the epoxy groups in said molding powder.

13. A molding powder in accordance with Claim 10 wherein said anhydride is employed in an amount which provides about 0.6 to about 0.9 anhydride groups per each epoxy group in the molding powder.

14. A molding powder in accordance with Claim 10 wherein at least a minor portion but not more than of said methyl methacrylate is replaced with a monomer selected from the group consisting of styrene, alpha-methyl styrene, vinyl acetate and an ester of acrylic or methacrylic acid and a monohydric alcohol other than methanol.

15. A molding powder in accordance with Claim wherein particulate, reinforcing filler is intimately dispersed with said copolymer and said monomeric anhydride.

16. A molded article having glass transition temperature above 90 C., fiexural strength above about 16,000 p.s.i., fiexural modulus above about 1.2 10 p.s.i. and elongation-to-break above 1 percent and formed from a molding powder which comprises a particulate intimate mixture of (a) a copolymer (1) consisting of about to about 40 weight percent glycidyl methacrylate, about 10 to about 30 weight percent methacrylonitrile and a remainder consisting essentially of methyl methacrylate, and

(2) having an average molecular weight in the range of about 1,500 to about 16,000, with less than 5 percent of the molecules of said copolymer having a molecular weight below 1,000, a softening point above 25 C., and epoxide groups in its molecular structure resultant of inclusion of said glycidyl methacrylate as a constituent monomer thereof, and

(b) a monomeric anhydride present in the amount which provides about 0.5 to about 1.5 anhydride groups per each epoxy group in the molding powder.

17. A molded article in accordance with Claim 16 wherein said copolymer has an average molecular weight in the range of about 2,000 to about 10,000.

18. A molded article in accordance with Claim 16 wherein said copolymer has an average molecular weight in the range of about 3,500 to about 8,000.

19. A molded article in accordance with Claim 16 wherein said monomeric anhydride is an anhydride selected from 1) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhydride group is directly attached to one of a pair of carbon atoms which are directly attached to and adjacent to each other,

(2) monomeric anhydrides of acyclic dicarboxylic acids wherein each carbon atom in an anhydride group is directly attached to one of a pair of carbon atoms which are separated by at least one carbon atom, and

(3) monomeric anhydrides of cyclic di-, tri-, or tetracarboxylic acids wherein each carbon atom of an anhydride group is directly attached to one of a pair of directly attached and adjacent carbon atoms of a C -C ring structure.

20. A molded article in accordance with Claim 16 wherein said monomeric anhydride is employed in an amount which provides about 0.6 to about 0.9 anhydride groups per each epoxy group in the molding powder.

21. A molded article in accordance with Claim 16 wherein in addition to said copolymer there is employed a diepoxide having a molecular weight in the range of about 300 to about 4,000 and a viscosity at 140 C. of less than poises, said diepoxide being employed in an amount providing between about 2 and about 20 percent of the epoxy groups in said molding powder.

22. A molded article in accordance with Claim 16 wherein at least a minor portion but not more than of said methyl methacrylate is replaced with a monomer selected from the group consisting of styrene, alpha-methyl styrene, vinyl acetate and an ester of acrylic or methacrylic and a monohydric alcohol other than methanol.

23. A molded article in accordance with Claim 16 wherein said article contains particulate, reinforcing filler which is intimately dispersed with said copolymer and said monomeric anhydride.

24. A molded article in accordance with Claim 16 wherein said article contains glass fibers which are intimately dispersed with said copolymer and said monomeric anhydride.

References Cited UNITED STATES PATENTS 2,580,901 1/ 1952 Erickson et a1. 26080.72 3,405,088 10/1968 Slocum 26041 A 3,201,497 8/1965 Heino 26080.72 X 2,556,075 6/1951 Erickson 26080.72 X 3,652,476 3/1972 Fellers et al. 26080.72 X

OTHER REFERENCES Lee et al.: Handbook of Epoxy Resins, McGraw-Hill Co., 1967, pp. 12-2, 5, 6, 7, 13, 14, 15, 16, 22, 23, 27, 36; 15-19, 20; 163, 5, 7.

LEWIS T. JACOBS, Primary Examiner US. Cl. X.R. 26080.72, 837 

1. A MOLDING POWDER WHICH COMPRISES A PARTICULATE, INTIMATE MIXTURE OF (A) A COPOLYMER (1) CONSISTING OF ABOUT 15 TO ABOUT 40 WEIGHT PERCENT GLYCIDYL METHACRYLATE, ABOUT 10 TO ABOUT 30 WEIGHT PERCENT METHACRYLATE, AND A REMAINDER CONSISTING ESSENTIALLY OF METHYL METHACRYLATE, AND (2) HAVING AN AVERAGE MOLECULAR WEIGHT IN THE RANGE OF ABOUT 1,500 TO ABOUT 16,000, WITH LESS THAN 5 PERCENT OF THE MOLECULES OF SUCH COPOLYMER HAVING A MOLECULAR WEIGHT BELOW 1,000, A SOFTENING POINT ABOVE 25:C., AND EPOXIDE GROUPS IN ITS MOLECULAR STRUCTURE RESULTANT OF INCLUSION OF SAID GLYCIDYL METHACRYLATE AS A CONSTITUENT MONOMER THEREOF, AND (B) A MONOMERIC ANHYDRATE PRESENT IN AN AMOUNT WHICH PROVIDES ABOUT 0.5 TO ABOUT 1.5 ANHYDRIDE GROUPS PER EACH EPOXY GROUP IN THE MOLDING POWDER. 